This invention relates to radio communications in general, and more particularly to ground-based relays for such communications.
Radio communications provide the ability to transmit voice and/or data between two remote locations (or xe2x80x9cstationsxe2x80x9d). These stations may be stationary or mobile. The stationary station(s) may be xe2x80x9cfreestandingxe2x80x9d, or they may be tied into a larger communications network via a ground-based relay.
By way of example, in FIG. 1 there is shown one such communications system, e.g., a cellular telephone system. More particularly, there is shown a mobile station 5 (e.g., an automobile) having a radio frequency (RF) transmitter 10 (e.g., a cellular telephone), and a stationary station 15 (e.g., a xe2x80x9ccell towerxe2x80x9d) having a RF receiver 20 (e.g., a cellular telephone receiver). Stationary station 15 is itself tied into a larger communications network 25 (e.g., the telephone system) by way of a ground-based relay 30.
In some circumstances, stationary station 15 may be located in a readily accessible area, e.g., the top of a building. In other situations, stationary station 15 may be situated in a relatively remote and/or hostile environment, e.g., at the top of a mountain, etc. These locations can make it difficult to provide abundant power to stationary station 15, RF receiver 20 and relay 30. In this respect it should be appreciated that, depending on the nature of its operation, relay 30 frequently requires substantial amounts of power to operate. This can present serious challenges to system designers.
As a result, one object of the present invention is to provide an improved low power relay which minimizes the power required to relay radio communications between an RF receiver and a larger communications network.
And another object of the present invention is to provide an improved relay which can also be used to supply power from a larger communications network to an RF receiver, the relay, etc.
These and other objects of the present invention are addressed by the present invention which, in one preferred embodiment, comprises a light modulator comprising a first mirror comprising a quarter-wave mirror stack comprising high reflectivity p+ type InP/InGaAsP layers; a Franz-Keldysh layer adjacent the first mirror, the Franz-Keldysh layer comprising i-InGaAsP; a second mirror adjacent the Franz-Keldysh layer, the second mirror comprising a quarter-wave mirror stack comprising low reflectivity n+ top, p+ type InP/InGaAsP layers; and a base layer adjacent the second mirror, the base layer comprising n+ type InP material.